Method and apparatus for cooling and guiding strands in continuous casting machines

ABSTRACT

In continuous casting, the cast strand which emerges from the casting mold is conducted through a secondary cooling zone wherein it is guided and supported between latticed guide plates having guide faces which contact areas of the surface of the casting which are supported thereby, and having windows therethrough bounded by said guide faces. The unsupported areas of the surface of the casting which are exposed by said windows are cooled by sprays of cooling water from spray nozzles located in the windows.

Unite 1 States Patent 1 1 [111 3,753,459 Burkhardt et al. Aug. 21, 1973 METHOD AND APPARATUS FOR COOLING 2,698,467 1/1955 Tarquinee et al 164/89 AND GUIDING STRANDS IN CONTINUOUS 3,39l,725 7/l968 Rossi 3,399,716 9/1968 ROSSI et al. 164 89 CASTING MACHINES [75] Inventors: Max Burkhardt, Zurich; Armin FOREIGN PATENTS OR APPLICATIONS Thalmann, s Ferdinand Fiala, 702,719 1 1954 Great Britain 164/283 Thalwil; Markus Schmid, Zurich, all 759,290 10/1956 'Great Britain 164/89 of Switzerland 9 [73] Assignee: Concast AG, Zurich, Switzerland Primary mine -R Spencer Annear -N'hlM.S d t 1. 221 Filed: Aug.30, 1971 Attorney a 21 A 1.19.; 176,107 1 pp 57 ABSTRACT In continuous casting, the cast strand which emerges [30] Foreign Application Priority Data from the casting mold is conducted through a second- Sept. 4, 1970 Switzerland 13266/70 ary cooling zone wherein it is guided and supported be- [52] U S Cl 164/89 l64/282 164/283 tween latticed guide plates having guide faces which [51] Bzzd 11/12 contact areas of the surface of the casting which are [58] Fie'ld 89 282 supported thereby, and having windows therethrough bounded by said guide faces. The unsupported areas of the surface of the casting which are exposed by said [56] References Cited windows are cooled by sprays of cooling water from UNITED STATES PATENTS spray nozzles located in the windows. 2,284,503 5/1942 Williams l64/282 16 Claims, 5 Drawing Figures 14 \J z/ a J 8 1 1 5 i 2i y q I 11 8 PATENTED M18 21 I975 SHEEI 1 0F 2 PAlENlEuAuszl ms SHEET 2 0f 2 METHOD AND APPARATUS FOR COOLING AND GUIDING STRANDS IN CONTINUOUS CASTING MACHINES This invention relates to a method and apparatus for cooling and guiding a continuous casting in the secondary cooling zone of a continuous casting machine, comprising guiding the casting between guide elements contacting opposite sides of the casting and cooling the casting by spraying areas of the casting exposed by windows in said guide elements.

In continuous machines it is conventional to guide the casting in the secondary cooling zone between rollers which are spaced from each other in the direction in which the casting moves. Disposed between the rollers are spray nozzles which spray the casting directly with cooling water and cool it. Due to the ferrostatic pressure in the casting and the required mechanical strength of the roller material, the rollers must have a reasonably large diameter which, on the one hand, determines the roller spacing, and on the other hand determines the spacing of the spray nozzles in the direction of travel of the casting. In casting machines for the casting of large cross sections, this results in large areas of the casting surfaces remaining unsupported between the rollers and in an insufficient rate of abstraction of heat from those areas because of the wide spacing required for the spray nozzles which are located between the rollers. This has the drawback of either causing the formation of bulges in the casting and the possible occurrence of metal break-outs or of requiring that the casting rate be kept so low that the resultant thicker frozen shell will not be deformed or broken by the ferrostatic pressure in the casting. Consequently, such machines cannot be used for casting large cross sections, such as slabs, at high casting speeds.

In another known arrangement for cooling, a short copper mold in which cooling is indirect is followed by a cooling grate of roughly the same length as the mold. This cooling grate is connected to the short mold and has guide rails extending in the longitudinal direction of the casting. Fan-spray nozzles mounted in the horizontal banks between the rails spray water with considerable kinetic energy against the casting. The difficulty with this arrangement is that only a relatively narrow region is intensely cooled by the spray jets, and that the cooling water that flows down the casting impairs and interferes with the cooling effect of the jets. Moreover, the cooling of the casting between and underneath the elongated guide rails varies considerably and the resultant casting may show faults.

It is an object of the present invention to abstract as must heat as possible from the casting in the secondary cooling zone by intense cooling, while at the same time providing maximum support to the casting to prevent bulging and metal break-out at high casting speeds. 7

According to the invention this object is achieved by cooling the moving casting by spraying unsupported surface areas that alternate in the longitudinal and transverse directions with supported surface areas for guiding the casting, said supported surface areas being kept substantially free from water.

This method provides a desirable combination of guidance and cooling for continuous casting, since cooled and guided surface areas alternate along the length and width of the casting in close side-by-side and up-anddown juxaposition.

The proposed apparatus for performing this method is characterized by the fact that the guide elements are lattice-like plates having guiding surface areas facing and contacting the opposed surface areas of the casting and conforming therewith in shape, said plates in both the longitudinal and transverse directions being provided with windows between the guiding surface areas which face the unsupported surface areas of the casting. Spray nozzles are located at the windows for spraying cooling water onto the surfaces of the casting which are exposed through the windows.

The presence of multiple guiding surface areas extending in the longitudinal direction of the casting prevents the most serious bulging since in the cross-wise direction the casting has only relatively short unsupported surface areas. With the use of roller guide means previously described, on the other hand, the unsupported widths may be as wide as about 2 metres. Furthermore, since cooling water is applied directly to these short surface areas a very intense cooling effect is provided'even in the immediate neighborhood of the supported surfaces. Also the method of alternately cooling and supporting the casting surface in the lengthwise direction utilizes the available casting surface to the best advantage. Since a withdrawing unit withdraws the casting downstream between two facing guide elements on opposite sides of the casting each part of the casting surface which has just been sprayed moves then downstream under a transverse guiding surface and thus becomes a supported surface. Since the supported surfaces of the casting are kept substantially free from water, the frozen shell can recover from the preceding intense spray cooling effect, thus avoiding the possibility of cracking the shell due to an excessively high cooling rate. It is also to be noted that the proposed method supports and guides substantial areas of the surface of the casting and not merely a narrow transverse line as with a roller support.

It is advantageous if the size of the area wetted by the spray nozzles corresponds roughly to the area of the unsupported surface. This can be achieved in various ways, as for example, by the choice of spray noules having a spray cone of suitable aperture, by adjustment of the distance of the spray nozzles from the surface of the casting and so forth. Cooled and supported surfaces will thus directly adjoin. It is also advantageous to provide that the sprayed water should also wet those parts of the supporting guiding elements above and on each side of the nozzle that are located close to the casting in order to cool these parts that are in continuous contact with the hot casting.

lt is further possible to spray the casting with spray nozzles that are closely adjacent in the transverse direction so that the surfaces wetted by adjacent nozzles are contiguous and together substantially cover the unsupported surface area. This is particularly advantageous for areas of the casting where no support is needed, as for example along the areas near the edges of slab castings where the risk of bulging is very much less. The omission of a guiding surface between the wetted surfaces permits the surface of the casting to be more efficiently cooled.

It is also important that the water sprayed on the casting should be drained away rapidly to prevent it from interfering with the cooling effect of the water spray. Since a transverse guiding surface directly below a nozzle makes contact with the casting, water may tend to accumulate above its edge and prevent the casting surface from being sprayed as desired. Arrangements should be made, therefore, to ensure that the spraying does not interfere with the draining of the water. For this purpose, the angle of the spray cone of the nozzle or the nozzle setting may be so chosen that the surface wetted by the spray does not extend completely to the transverse guiding surface below the nozzle, i.e. so that the spray cone does not quite reach the latter. Furthermore, the lower walls of the windows behind which the nozzles are mounted are preferably arranged to slope downwards away from the casting at an angle between about and 25 so that the sprayed water will first flow a short distance down the casting before running down the sloped lower wall. This water should not be allowed to interfere with the spray cone of the next nozzle in the direction of movement of the casting, and it should therefore also be deflected away from the next spray cone underneath. Drain holes may be provided to facilitate the removal of this water. For this purpose the transverse walls of the windows are preferably extended beyond the spray nozzles underneath, and drain holes through the walls are preferably located further away from the casting than the nozzle.

The method of the invention will be particularly effective if the casting moves across a plurality of consecutive rows of windows separated by the supported surfaces, and especially if the windows of consecutive rows are staggered relative to each other.

As the casting moves across the previously described lattice type cooling apparatus the unsupported width of the casting surface can be continuously changed if the lattice-like guiding surfaces are arranged to extend obliquely across the direction of travel of the casting. By such continuous change between supported and unsupported surface areas the cooling of the casting can be rendered even more uniform.

V The cost of producing and maintaining such lattices can be reduced and the use of highly wear-resistant materials substantially simplified if the plates from which the lattices are formed are divided into component plates which are interchangeably mounted in a supporting framework.

A wear-resistant cast iron has proved to be a very satisfactory material for making the lattice plates since it combines favorable properties with regard to strength and abrasion while being resistant to heat damage. In the case of slab casting machines it is advantageous to guide and cool only the broad sides of the slabs by means of such lattices, for hinged deflector plates for shedding the water have been found adequate for the narrow sides.

If the casting program calls for the production of consecutive castings of different cross sections, the facing plates on opposite sides of the casting may be adjusted to comply with the required cross sections..Adjustment may be accomplished by using conventional means of a hydraulic or mechanical nature, such as hydraulic rams adapted to advance the guide plates up to limit stops, or thrust and draw bolts. Such devices also permit the desired path of the casting to be adjustably controlled within limits.

Other features of the invention will be understood from the following description of embodiments of the invention which relate to the continuous casting of steel slabs. In the drawing FIG. 1 is a schematic vertical section through a casting machine having guide elements according to the invention.

FIG. 2 is a fragmentary plan view of a guide element.

FIG. 3 is a section taken on the line IIIIII in FIG.

FIG. 4 is a section taken on the line IVIV in FIG. 2, and

FIG. 5 is a plan view of part of a modified form of guide element.

Referring to FIG. 1, molten steel is poured from a tundish 1 into a water-cooled mold 2. Disposed below the mold 2 are the guide elements 3, 3' and 4, 4' which are arranged in pairs to bear against opposite sides of the casting 5 that has been formed in the mold 2. The casting 5 straightening withdrawn from the machine by a withdrawing and straightenein unit 6. During its passage between the guide elements, the casting is cooled by being sprayed with water from spray nozzles 8.

FIGS. 2, 3 and 4 show details of this arrangement. FIG. 2 is a fragmentary plan view of a guide element consisting of a lattice-like plate 3", preferably of a wear-resistant cast iron. The plate 3" has guide faces 10 which bear against the surface of the casting and is provided with spaced windows 11. In the region of the windows the surface areas 16 of the casting are unsupported. As shown in FIG. 3 the guide faces 10 are in contact with and support the casting 5 which in this region has not yet completely solified and encloses a liquid core 14 contained in a relatively thin frozen shell 15.

Spray nozzles 8 are disposed in the windows 11 to spray cooling water onto the unsupported surface areas 16 so that the casting is alternately sprayed and supported in both the longitudinal direction 18 and transverse direction 19. The size of the sprayed surface area is so chosen that it roughly corresponds to the size of the windows 11. This can be achieved by choosing suitable nozzles and by adjusting their distance from the surface of the casting. It is important that the supported surface area of the casting be kept substantially free from water to avoid an uncontrolled cooling effect. As shown in FIG. 2, the windows 11 in the lattice-like plates are square, and it is assumed that nozzles are used that deliver a full spray cone so that the sprayed area of the surface is circular. Moreover, as shown in FIG. 3, the nozzles are so adjusted that a narrow unsprayed region 20 remains between the guide surface 10 and the sprayed surface. This prevents the spray cone from being disturbed by accumulated water. Furthermore, as shown in FIG. 3, the bottom walls 21 slope rearwardly and downwardly away from the casting at an angle 22 and therefore allow inadvertently accumulating water to flow away. The walls may also contain holes 23 through which the water can drain. In the illustrated embodiment the angle 22 is about 15, but it may be any angle between l0 and 25 depending upon the cross section of the casting and the volume of cooling water required. To ensure that there is no interference between sprays from adjacent nozzles, the mouth of each spray nozzle is located within the walls that surround it. It is important that the rear portions of the walls 21 extend beyond the spray nozzles and that the drain holes 23 be located further away from the casting 5 than the nozzle. If desired, the side of the plate 3" facing the casting 5 may be subdivided, as shown in FIG. 2, into readily replaceable component plates 30,

30 which are mounted on a supporting framework 31.

F108. 2 and 4 illustrate how the plate 3" is held by and attached to the steel framework. A member 25 which projects from frame 24 engages a window 26 in the edge of plate 3 and thereby supports the plate. The plate is held in fixed position on the frame by two thrust bolts 27. in order to change the spacing between two guide elements on opposite sides of a casting when the cross section of the casting is to be changed, a draw bolt 28 is provided. The adjustment of the spacing could be effected by other means, such as hydraulic devices cooperating with stops.

FIG. 5 is a plan view of a plate having guide surfaces that extend at an oblique angle to the direction of movement of the casting. These oblique guide surfaces have the advantage of reducing the risk that projecting parts of the casting may be intercepted and that the casting surface may be torn open thereby as it moves across the guide surfaces.

If desired, the windows may be circular or elliptical or otherwise shaped to conform to any particular shape of surface sprayed by a nozzle. In order to reduce the unsupported length of surface area on the moving casting as much as possible, the windows nearest the mold may be in the form of wide slots extending across the direction of movement of the casting, and cooling may be effected by fan-type spray nozzles. Optimum cooling can thus be achieved while the surface is at the same time afforded maximum support.

If desired, the guide plates may be attached to the mold and participate in the customary mold oscillation. In this case the gap between mold and the guide plates, which otherwise continuously changes in width, remains constant, a factor which likewise assists in reducing the risk of metal break-out.

We claim as our invention:

1. A method of cooling and guiding a continuous casting in the secondary cooling zone of a continuous casting machine, which comprises forming a continuous embryo casting in a chilled mold, guiding the casting between guide elements located downstream'from said mold, said guide elements having latticed guide faces contacting areas of the surface of the casting which are supported thereby, and cooling the moving casting by spraying with cooling water only the unsupported areas of the surface of the casting that alternate in both the longitudinal and transverse directions with said supported surface areas for guiding the casting, removing the sprayed waterto keep said supported surface areas being kept substantially free from water.

2. A method according to claim 1, which is characterized in that any excess of sprayed water is drained off to the rear away from the casting to a point outside the spray cone which follows in the direction of movement of the casting.

3. A method according to claim 1, which is characterized in that an unsupported surface area of the casting is sprayed with cooling water supplied from two adjacent spray nozzles, the contiguous sprayed surface areas wetted thereby together substantially cover said unsupported surface area.

4. A method according to claim 1, which is characterized in that the guide faces above and on both sides of the nozzle are cooled by sprayed water and that a small region near the bottom guide face is not directly exposed to the sprayed water.

5. Apparatus for cooling and guiding a continuous casting in the secondary cooling zone located downstream from the mold of a continuous casting machine, comprising a pair of opposed guide elements each comprising latticed guide plates with faces for contacting areas of the surface of the casting which are supported thereby, said guide plates having windows therethrough which are bounded by said guide faces, and spray nozzles located in said windows between said guide faces for spraying cooling water through said windows onto the un-supported areas only of the surface of the casting which are exposed thereby, said window areas being shaped to keep said contacting areas substantlally free of water.

6. Apparatus according to claim 5, in which each of said guide plates contains at least two rows of windows which are consecutive in the direction of motion of the casting and which are separated by a guide face.

7. Apparatus according to claim 6, in which the windows in consecutive rows are staggered relative to each other.

8. Apparatus according to claim 5, in which the wetted area of the casting surface sprayed by the spray cone corresponds substantially to the unsupported casting surface.

9. Apparatus according to claim 5, in which the bottom wall of the window slopes downwards to the rear away from the casting at an angle.

10. Apparatus according to claim 9, in which the angle of slope is between 10 and 25 11. Apparatus according to claim 9, in which said bottom wall contains at least one hole for draining off accumulating water.

12. Apparatus according to claim 9, in which the rear edge of the bottom wall extends beyond the spray nozzle away from the casting.

13. Apparatus according to claim 5, in which the latticelike guide faces are obliquely inclined to the direction of movement of the casting.

14. Apparatus according to claim 5, in which the latticelike guide plates are divided across the width of the casting into component plates and are replaceably attached to a supporting framework.

15. Apparatus according to claim 5, in which the latticelike guide plates consist of a wear-resistant cast ll'Ol'l.

16. Apparatus according to claim 5, in which the spacing between facing guide plates on opposite sides of the casting is adjustable. 

1. A method of cooling and guiding a continuous casting in the secondary cooling zone of a continuous casting machine, which comprises forming a continuous embryo casting in a chilled mold, guiding the casting between guide elements located downstream from said mold, said guide elements having latticed guide faces contacting areas of the surface of the casting which are supported thereby, and cooling the moving casting by spraying with cooling water only the unsupported areas of the surface of the casting that alternate in both the longitudinal and transverse directions with said supported surface areas for guiding the casting, removing the sprayed water to keep said supported surface areas being kept substantially free from water.
 2. A method according to claim 1, which is characterized in that any excess of sprayed water is drained off to the rear away from the casting to a point outside the spray cone which follows in the direction of movement of the casting.
 3. A method according to claim 1, which is characterized in that an unsupported surface area of the casting is sprayed with cooling water supplied from two adjacent spray nozzles, the contiguous sprayed surface areas wetted thereby together substantially cover said unsupported surface area.
 4. A method according to claim 1, which is characterized in that the guide faces above and on both sides of the nozzle are cooled by sprayed water and that a small region near the bottom guide face is not directly exposed to the sprayed water.
 5. Apparatus for cooling and guiding a continuous casting in the secondary cooling zone located down-stream from the mold of a continuous casting machine, comprising a pair of opposed guide elements each comprising latticed guide plates with faces for contacting areas of the surface of the casting which are supported thereby, said guide plates having windows therethrough which are bounded by said guide faces, and spray nozzles located in said windows between said guide faces for spraying cooling water through said windows onto the un-supported areas only of the surface of the casting which are exposed thereby, said window areas being shaped to keep said contacting areas substantially free of water.
 6. Apparatus according to claim 5, in which each of said guide plates contains at least two rows of windows which are consecutive in the direction of motion of the casting and which are separated by a guide face.
 7. Apparatus according to claim 6, in which the windows in consecutive rows are staggered relative to each other.
 8. Apparatus according to claim 5, in which the wetted area of the casting surface sprayed by the spray cone corresponds substantially to the unsupported casting surface.
 9. Apparatus according to claim 5, in which the bottom wall of the window slopes downwards to the rear away from the casting at an angle.
 10. Apparatus according to claim 9, in which the angle of slope is between 10* and 25* .
 11. Apparatus according to claim 9, in which said bottom wall contains at least one hole for draining off accumulating water.
 12. ApparatUs according to claim 9, in which the rear edge of the bottom wall extends beyond the spray nozzle away from the casting.
 13. Apparatus according to claim 5, in which the latticelike guide faces are obliquely inclined to the direction of movement of the casting.
 14. Apparatus according to claim 5, in which the latticelike guide plates are divided across the width of the casting into component plates and are replaceably attached to a supporting framework.
 15. Apparatus according to claim 5, in which the latticelike guide plates consist of a wear-resistant cast iron.
 16. Apparatus according to claim 5, in which the spacing between facing guide plates on opposite sides of the casting is adjustable. 